X-ray fluorescent screen



May 14, 1963 7 3,089,956

WALTER J. HUSHLEY NOW BY CHANGE OF NAME WALTER JOHN HARPER X-RAY FLUORESCENT SCREEN Filed July 10, 1955 Fig. l.

Photogmissive Conductive (Boating 8 Matenal Material g 2 Photoemissive WITNESSES: INVENTOR Walter J. Hushley.

ATTORNEY United States Patent Ofiice 3,Q89,956 Patented May 14, 1963 3,089,956 X-RAY FLUORESCENT SCREEN Walter J. Hushley, now by change of name Walter John Harper, Pittsburgh, Pa, assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa, a corporation of Pennsylvania Filed July 10, 1953, Ser. No. 367,167 Claims. (Cl. 25tt80) My invention relates to fluorescent screens and in particular relates to a screen comprising both fluorescent material and photoelectric material which is capable of transforming an X-ray or other radiation image into an electron image which is its replica. Such screens are useful in image intensifiers, of which one typical example is to be found in Coltman and Masons U.S. Patent 2,523,132 issued September 19, 1950 and assigned to the assignee of this application.

In image intensifiers of the type just referred to an X- ray beam after passing through a pictured object is incident upon a screen having a thin layer of zinc sulphide separated from a thin layer of photoelectric material by a thin layer of glass. The light generated by the X-rays in the zinc sulphide causes the closely adjacent areas of the photoelectric material to emit electrons, thus forming an electron image which is accelerated electrically into incidence on an electron-phosphor screen where it produces a bright light image in replica of the X-ray distribution.

To attain a true reproduction of the fluorescent image the separation between the zinc sulphide particles and the photoelectric particles should be as small as possible. In my present invention this is achieved by forming the body of the screen of a chemically machined glass on which the zinc sulphide is mounted.

One object of my invention is, accordingly, to provide a new and improved form of optical screen for converting X-ray or other radiation images into electron images.

Another object is to provide an improved type of image screen for electronic image intensifier tubes.

Still another object is to provide an improved structure for mouting fluorescent materials in close contiguity to photoelectrically emissive material.

Other objects of my invention will become apparent upon reading the following description taken in connection with the drawings in which:

FIG. 1 is a mid-cross-sectional view of one form of image screen embodying the principles of my invention;

FIG. 2 is a similar view of another form of image screen in which such principles may be embodied; and

FIG. 3 is a similar view of a modified image screen.

Referring in detail to FIG. 1, the main body of the screen comprises the special glass which is becoming known as chemically machined glass, and is sold by the Corning Glass Company of Corning, New York. For the image screens to be used in X-ray image intensifiers currently marketed by applicants assignee it may have the form of a segment, six inches in diameter, of the surface of an eleven inch radius sphere. A peripheral rim 1 about half an inch wide and 50 mils thick gives strength and rigidity, while a grid of ribs 2 of the same thickness and 2 mils wide, enclosing square sockets 3 which are 63 mils on a side and 48 mils deeps, cross-connects points on this rim. The method I am acquainted with at the moment for making such a foraminated glass structure is by etching the sockets with a chemical reagent such as hydrofluoric acid in a spherical segment of the above-descibed glass 50 mils thick. This etching method is described in detail in Industrial and Engineering Chemistry, vol. 45, page 115, January 1953 and some previous articles, but any other method of producing a rigid structure having sockets of about the same dimensions each with a transverse septum about 2 mils thick of the aforesaid glass is within the scope of my invention.

The sockets are coated inside on the transvense wall only with a thin layer 4 of aluminum, e.g., by vapor condensation, and the outer face of the glass is coated with a thin layer 5 of a transparent electrical conductor, e.g., by hot-spraying with tin chloride. The sockets are then filled with zinc sulphide-silver or other suitable phosphor 6 such as that known under the trade name of Patterson B (sold by du Pont de Nemours, Wilmington, Delaware). This phosphor may comprise particles of about 45 microns average diameter and an amount of 200 to 250 mg. per square centimeter would fill the abovedescribed sockets. The remaining face of the sockets should be covered by a metal foil 7 such as aluminum about one mil thick. Adjacent the conductive coating 5 is shown a layer 8 of a suitable photoemissive material such as that disclosed in the above-mentioned Coltman and Mason U.S. Patent 2,523,132.

FIG. 2 shows another form of screen in accordance with my invention in which the square sockets of the FIG. 1 screen are replaced by square holes passing completely through the glass frame. The dimensions of the rim, side walls, coatings and openings may be the same as in FIG. 1. A separate thin sheet 11 of glass covers the concave face of the screen openings, and its outer face is coated with a transparent conductive layer 5. The holes are filled as in FIG. 1 with the phosphor 6 abovedescribed and their free face covered with the aluminum foil '7 as before. The use of a thin layer of glass between the aluminum layer 7 and the phosphor is also within the contemplation of my invention. Adjacent the conductive coating 5 is shown a layer 8 of a suitable photoemissive material such as that disclosed in the abovementioned Coltman and Mason U.S. Patent 2,523,132.

The holes need not be square but may be of any shape and their size and number may also be varied. FIG. 3 illustrates a modified structure in which the walls of the holes 3 are tapered.

I claim as my invention:

1. In an image amplifier, an input screen comprising a foraminated plate member of insulating material, said plate member having a foraminated surface and a nonforaminated surface, said plate member including a thin septum of said insulating material transverse to the foraminations therein, a layer of transparent conductive material upon said non foraminated surface of said plate member, fluorescent material filling each of said foraminations and a thin metallic member upon said foraminated surface of said plate member, said thin septum having a thickness of less than 10 percent of the thickness of said plate member.

2. In an image amplifier, an input screen comprising a foraminated plate member of insulating material, said plate member having a foraminated surface and a nonforaminated surface, said plate member including a thin septum of said insulating material transverse to the foraminations therein, a layer of transparent conductive material upon said non-foraminated surface of said plate member, a layer of photoelectric material upon said layer of transparent conductive material, fluorescent material filling each of said foraminations to obtain a fluorescent image therein, said thin septum being of a thickness to provide a true reproduction of said fluorescent image on said photoelectric layer and a thin metallic member upon said foraminated surface of said screen member.

3. In an image amplifier, an input screen comprising a foraminated plate member of insulating material, said plate member having a foraminated surface and a nonforaminated surface, said plate member including a thin septum of said insulating material transverse to the foraminations therein, a layer of transparent conductive ma terial upon said non-foraminated surface of said plate member, a layer of photoelectric material upon said layer of transparent conductive material, fluorescent material filling each of said foraminations, and a thin metallic member upon said foraminated surface of said screen member, said thin septum having a thickness of less than percent of the thickness of said plate member.

4. In an image amplifier, an input screen comprising a foraminated plate member of insulating material, said plate member having a foraminated surface and a nonforaminated surface, said plate member including a thin septum of said insulating material transverse to the forarn inations therein, a layer of transparent conductive material upon said nonforaminated surface of said plate member, fluorescent material filling each of said foraminations, said foraminations having side wall portions, a reflecting surface lining said side wall portions of said foraminations, and a thin metallic member upon said foraminated surface of said plate member.

5. In an image amplifier, an input screen comprising a foraminated plate member of insulating material, said plate member having a foraminated surface and a nonforaminated surface, said plate member including a thin septum of said insulating material transverse to the foraminations therein, a layer of transparent conductive material upon said non-foraminated surface of said plate member, a layer of photoelectric material upon said layer of transparent conductive material, fluorescent material filling each of said foraminations, said foraminations having side wall portions, a reflecting surface lining said side wall portions of said foraminations, and a thin metallic member upon said foraminated surface of said screen member.

6. In an image amplifier, an input screen comprising a foraminated plate member of insulating material, said plate member having a foraminated surface and a nonforaminated surface, said plate member including a thin septum of said insulating material transverse to the foraminations therein, a layer of photoelectric material upon the surface of said fluorescent screen member opposite said foraminated surface of said plate member, fluorescent material filling each of said foraminations, said foraminations having side wall portions, a reflecting surface lining said side wall portions of said foraminations, and a thin metallic member upon said foraminated surface of said plate member.

7. In an image amplifier, an input screen comprising a plate member of insulating material having a plurality of foraminations therein, said plate member including a thin transparent septum transverse to said foraminations so that said plate member has a foraminated surface and a non-foraminated surface, a layer of photoelectric material upon said non-foraminated surface and fluorescent material filling each of said foraminations to obtain a fluorescent image therein, said thin transparent septum being of a thickness to provide a true reproduction of said fluorescent image on said photoelectric layer.

8. In an image amplifier, an input screen comprising a plate member of insulating material having a plurality of foraminations therein, said plate member including a thin transparent septum transverse to said foraminations so that said plate member has a foraminated surface and a non-foraminated surface, a layer of photoelectric material upon said non-foraminated surface and fluorescent material filling each of said foraminations, said thin transparent septum providing a barrier of minimum thickness between said photoelectric mateiral and said fluorescent material, said thin septum having a thickness of about two mils.

9. An intensifying screen for X-ray registrations comprising a honeycomb-shaped grid, the walls of which are light-reflecting and the apertures of which are filled with a luminescent substance, said apertures being formed in a glass plate made of photographically sensitive glass and the partitions are coated with a light-reflecting metal layer.

10. An intensifying screen as claimed in claim 9, in which the partitions are tapered on both sides.

References Cited in the file of this patent UNITED STATES PATENTS 1,467,132 Bilstein Sept. 4, 1923 2,029,639 Schlesinger Feb. 4, 1936 2,303,563 Law Dec. 1, 1942 2,324,505 Iams et al July 20, 1943 2,501,376 Breadner et a1 Mar. 21, 1950 2,523,132 Mason et al Sept. 19, 1950 2,555,545 Hunter et al. June 5, 1951 2,567,714 Kaplan Sept. 11, 1951 2,582,822 Evans Jan. 15, 1952 2,583,000 Lytle Jan. 22, 1952 2,606,299 Coltman et al. Aug. 5, 1952 2,660,686 Putnam Nov. 24, 1953 2,689,189 Hushley Sept. 14, 1954 2,705,765 Geer Apr. 5, 1955 2,739,243 Sheldon Mar. 20, 1956 OTHER REFERENCES Fluoroscopic Image Brightening by Electronic Means, Coltman, Radiology, v01. 51, September 1948, pp. 359 366. 

1. IN AN IMAGE AMPLIFIER, AN INPUT SCREEN COMPRISING A FORAMINATED PLATE MEMBER OF INSULATING MATERIAL, SAID PLATE MEMBER HAVING A FORAMINATED SURFACE AND A NONFORAMINATED SURFACE, SAID PLATE MEMBER INCLUDING A THIN SEPTUM OF SAID INSULATING MATERIAL TRANSVERSES TO THE FORAMINATIONS THEREIN, A LAYER OF TRANSPARENT CONDUCTIVE 